Apparatus for producing high density plywood tubing



June 20, A l L 2,351,692

APPARATUS FOR PRODUCING HIGH DENSITY PLYwOOD TUBING Fild June 6, 1942 2 Sheets-Sheet 1 lav.

INVENTOR. Jo/m fl. M1458.

. J. A. MILLER June 20, 1944. 2,351,692 A APPARATUS FOR PRODUCING HIGH DENSITY PLYWOOD TUBING Filedv June 6, 1942 2 Sheets-Sheet 2 Patented June'20, 1944 APPARATUS FOR PRODUCING HIGH DENSITY PLYWOOD TUBING John A. Miller, De Kalb, Ill., assignorto The Budolph Wurlitzer Company, Chicago, 111,, a corporation Application June 6, 1942, Serial No. 446,100

6 Claims. (Cl. 144-268) This invention relates to an apparatus for producing high density plywood tubing through impregnation by suitable filler and compression through the application of high pressure while in a heated condition.

High density plywood tubing has great strength, is impervious to the elements and'has insulating qualities which adapt it to many structural uses. It may be of varying cross section, but is usually cylindrical, and also usually'o'f uniform diameter. Furthermore, the tubing may be formed through the spiral winding of wood veneer including the cross winding thereof where desired, or may be formed by lap winding, or any combination of straight lap winding and cross or direct spiral winding. The lapping or winding of the veneer to form the plywood tubing is accompanied by the application of the thermo-setting glue as a bonding material therefor. The wrappings of veneer may be entirely impregnated, or some of the veneer or laminae may be impregnated while some is unimpregnated, However, the density of the tubing is varied or controlled by the extent of the impregnation thereof so that it may be said that the more extensive the laminae is impregnated, the higher will be its density-all else being equal. Preferably the impregnation may comprise the application of a thermo-setting resin and its penetration of the wood fibres through the application of heat and pressure. Thus,

through suitable application and processing ofthe veneer with a thermo-setting resin, pressure under heat may be applied, such as to actually reduce the normal thickness 01 the plywood by fifty percent, with a corresponding increase in density. This may be accomplished by reason of the soft, compressible and flowing character of the fibres so treated with the impregnating material and the application of heat.

A feature of'this. invention resides in the ap-. paratus for applying external pressure in the forming of plywood-tubing for effecting the desired compression thereof.

Another feature of the invention resides in such application of external pressure while the tubing is subjecte to a highly heated condition. Another feature of the invention resides in the application of pressure to the surface of the tubing simultaneously with the application of heat thereto and while in a state of impregnation by a suitable material such as a thermosetting resin.

The full nature of the invention will be undering and providing the support and inner surface form for the plywood tubing to be compressed to high density. Thismandrel may be of varying shapes and cross section or tapered, depending upon the form and shape of tubing to be produced. It is adapted to receive the plywood tubing after being formed andtreated with the bonding and impregnating material. The tubing having been first formed, is preferably cut into sections of the desired length and mounted endwise of the mandrel l0, and within the loosened wrappings of a sheet metal protective shell I l and the wrapping member. The protective shell II is preferably formed of thin polished spring metal and is normally in loose cylindrical formation within which the tubing is conveniently inserted and covered so that the edges of the shell overlap as illustrated in Fig. 3.

The wrapping member, as illustrated in Fig. 2, is formed of thin spring steel having a body portion' l2 with laterally-extending strips l3 extending from opposite sides thereof and in staggered relation, each group of strips being of the same width as the spacing therebetween. The wrapping member is of such dimensions that for a given size tubing it will extend over the full length thereof and the body portion will wrap thereabout substantially one lap, whereas the strips l 3 will interlace with respect to each other and pass around the body portion and tubin with one lap before extending in opposite dlrections.

The mandrel III is supported upon or in relation to, in any suitable manner, a base plate I4 and is arranged to provide suitable heat for the tubing compressed thereon through anyrsuitable at one end of the base plate a lower clamping bar l8 and an upper clamping bar" between which I the ends l8 of the strips l3 may be clamped and upper clamping bar 2| to which the ends 22 of strips iii are secured by the screws 23. Said tension bar is provided with internally threaded sleeves 24 into each of which a threaded tension rod 25 extends. Each of said rods also extends through suitable sleeves 26 mounted on a crank block 21. The operative ends in each of said tension rods are provided with a crank handle 28. The base plate may be calibrated along opposite edges thereof for the purpose of indicating the compression to which the plywood tubing 30 has been subjected and to control the extent of come pression at opposite ends thereof.

The wrapped veneer or plywood tubing may be subjected tosuch pressure by the wrappings and drawing apart of the strips of the wrapping member as to eflect a compression thereof controlled by the positioning of the tension bar, and wherein the fibres have been rendered soft and pliable through the impregnation thereof by the plastic under such heat as to cause a certain amount tubing and having oppositely extending strips in spaced and staggered relation adapted to interlace to extend in opposite directions, a fixed clamping member to which the strips on one side of the tubing are secured, a movable clamping member secured to the oppositely-extending strips, and means for drawing said movable clamping member to app y suillcient tension to said strips to compress the plywood to a fraction of its normal thickness.

2. Apparatus for producing high density plywood tubingcomprising a mandrel over which preformed plywood tubing is mounted, means associated with said mandrel for heating the tubing thereon, a sheet metal wrapp member having a body portion overlying and extending about the tubing, said body portion being formed with a series of integral and laterally-extending strips spaced from each other and formed in staggered relation on opposite sides of said body portion, means for anchoring the strips on one side of said body portion, and means for exerting tension on the oppositely-extending strips for drawing the body portion taut to apply pressure about the tubing to compress the plywood thereof to a fraction of its normal thickness.

3. Apparatus for producing high density plywood tubing comprising a mandrel over which preformed plywood tubing is mounted, means aaeaeee associated with said me idrel for heating the tubing thereon, a sheet metal shell surrounding said tubing with its edges overlapping, a wrapping member surrounding said shell and having a body portion and oppositely extending interlaced strips, a base plate, a clamp on said base plate for anchoring the strips extending from one side of said body portion, a tension bar secured to the strips extending from the opposite side of said body portion, and means on said base plate for exerting force on said tension bar sufiicient to draw said wrapping member taut about the tubing for exerting sufficient pressure thereabout to compress the plywood to a fraction of its normal thickness. 4. Apparatus for producing high density plywood tubing comprising a mandrel over which preformed plywood tubing is mounted, means associated with said mandrel for heating the tubing thereon, a sheet metal shell surrounding said tubing with its edges overlapping, a wrapping member surrounding said shell and having a body portion and oppositely extending interlaced strips, a base plate, a clamp on said base plate for anchoring the strips extending from one side of said body portion, a tension bar secured to the strips extending from the opposite side of said body portion, means on said base plate for exerting force on said tension bar sufficient to draw said wrapping member taut about the tubing for exerting sufiicient pressure thereabout to compress the plywood to a fraction of its normal thickness. and tension registering means associated with I said tension bar for indicating the pressure applied at opposite ends of the tubing.

5. Apparatu for producing high density plywood tubing, comprising a mandrel over which preformed plywood tubing is mounted, a sheet metal wrapping surrounding the tubing and having oppositely extending strips arranged in spaced and staggered relation adapted to interlace for permitting them to extend in opposite directions from said wrapping, and means connected with said strips operable to draw them in their respective opposite directions and thereby apply sufilcient tension to said strips and wrapping to compress the plywood to a fraction of its normal thickness.

6. Apparatus for producing high density plywood tubing, comprising a mandrel over which preformed plywood tubing is mounted, a sheet metal shell surrounding said'tubing, a wrapping member surrounding said shell and having a body portion with outwardly extending interlaced strips extending in opposite'directions, and means connected with said oppositely extending strips 

